1. Field of Invention
The present invention relates generally to blood-gas analysis and more particularly to a blood-gas sampler comprising a syringe having novel seal, barrel and plunger fittings to accommodate entry of blood into the barrel under force of arterial pressure and discharge of blood from the barrel while avoiding seal set due to protracted shelf storage of the assembled syringe.
2. Prior Art
Prior art blood-gas sampling syringes have utilized relatively unsatisfactory seals interposed between the plunger and the barrel of the syringe. Most frequently the syringe barrels are glass, but occasionally of plastic. The mentioned seals are of a relatively hard elastomer and consist primarily of a single seal comprising two or three annularly enlarged rings each being deformed against the inside surface of the barrel creating a relatively wide high fricton sealing contact with the interior surface of the barrel. With such deformed seals storage over a protracted interval of time results in the elastomer of the seal taking a set. Thereafter, the required pliance no longer exists for the seal to conform to and follow the interior surface of the barrel. Accordingly, leaking of air and/or blood across the seal occurs, which renders inaccurate results when the blood-gas characteristics of the blood sample are tested. The subject matter of my prior U.S. Pat. No. 3,890,956 afforded the use of one sealing ring during aspiration and two during discharge but did not solve or attempt to solve the leakage problem due to seal set.